1. Field of the Invention
This invention relates generally to a curved, shatterproof glass laminate, wherein at least one glass layer of the laminate is selected from the group consisting of heat tempered, heat strengthened and annealed glass, and a method of forming the laminate, and more particularly to a curved, shatterproof glass laminate for use in the form of an automotive or other transportation vehicle windshield, side window, back window or sun roof, and a method of forming the laminate precisely and economically in large quantities, with excellent optical qualities and other desirable physical characteristics, utilizing a rigid, structurally stable, quick-releasable and reusable hard plastic or metal mold member, or an elastic, flexible resin-reinforced fiber glass mold member.
2. Description of Related Art
At the present time, it is standard practice to make windshields of automotive vehicles of shatterproof construction to prevent injury to a vehicle occupant in the event of a collision, particularly as a result of the occupant's head moving forward and striking the windshield. Typically, a windshield may be constructed in the form of a curved laminate comprising a plastic shock or energy absorbing-adhesive layer between two silicate glass layers. It also is known to provide an antilacerative plastic layer on the interior glass layer of the windshield to prevent occupant injury from glass shards or splinters. In another form, the windshield may comprise an outer silicate glass layer, an adhesive inner layer and an interior-facing plastic layer.
However, a serious problem exists in known windshields, and in particular, the type of windows still generally used in automotive and other transportation vehicles, such as buses, trucks and trains, i.e., the side windows and/or back windows, and including sun roofs, in that these windows still are readily subject to breakage, either as a result of a collision and/or vandalism. For example, the side windows, which are those generally chosen by vandals for obtaining access into the vehicle, generally are formed of a single sheet of heat tempered glass. Further, when one of these windows is shattered, either in a collision or by a hammer, iron bar, rock or other manual weapons, splinters and shards of glass tend to be propelled into the interior of the vehicle, with possible serious injury to the occupant(s). The ease with which such a window can be shattered also invites widespread vandalism and/or personal attacks upon the vehicle occupant(s), including shooting through the window, further contributing to the problem of individual personal safety.
Accordingly, a particular need exists for a vehicle window which is substantially more resistant to impact, including gun shots, does not shatter and propel glass fragments into the interior of the vehicle, has excellent optical qualities and other desirable physical characteristics, and is of a configuration and thickness such that it readily can be mounted in an existing vehicle window frame or holder for either replacement or new manufacture purposes, without any substantial modification of the existing frame or holder.
A primary purpose of the subject invention, therefore, is to provide a new and improved curved, shatterproof glass laminate construction in the form of a windshield or a vehicle window, such as a side window, back window or sun roof, and a new and improved method of forming the laminate, which satisfy these criteria.
In general, as noted previously, the forming of curved glass-plastic laminates is known. For example, U.S. Pat. No. 3,806,387 to Peetz et al. discloses the forming of a bent or curved safety glazing or laminate for a windshield, comprising a sheet of ordinary silicate glass, an adhesive layer such as a sheet of polyvinyl butyral resin, and a plastic sheet of cellulose acetate butyrate. To improve the optical qualities of the formed laminate, a curved protective member in the form of a second glass sheet, having a configuration conforming to that of the first glass sheet, is positioned in pressure engagement with the plastic sheet, in combination with a demolding agent. The resultant assembly then is subjected to vacuum degasification, heat and pressure in an autoclave to form the laminate, after which the glass protective member is removed.
In the U.S. Pat. No. 3,933,552 to Shumaker, a laminated safety glass panel is disclosed, comprising sheets of rigid transparent material, such as glass, polycarbonate, polyester and the like, alternating with interlayer materials, such as polyvinvyl butyral, polyurethane and the like. The sheets of transparent material are subjected to a preprocessing method which involves a combination of roll pressing and peripheral evacuation. The preprocessing occurs prior to a final laminating step wherein the preprocessed assembly is subjected to elevated temperature and pressure while in an autoclave. The patent further suggests that the assembly may include additional alternate layers of relatively rigid transparent material and relatively flexible material to provide-an assembly of more or less than three layers to be laminated to form a transparent safety window closure. Further, it is indicated that one or more of the rigid transparent sheets of glass may be made of any of the commonly known glass substitutes such as polycarbonates, acrylic plastic, polyesters and the like. The laminated structure can also include tempered glass.
U.S. Pat. No. 3,960,627 to Halberschmidt et al. involves a glazing or laminate including a sheet of glass and a sheet of plastic adhesively fastened thereto, and represents an improvement over the use of the contoured glass protective member of the above-mentioned Peetz et al. patent. It is indicated that a glass protective member is undesirable for various reasons, including a tendency to adhere to the laminate being formed, resulting in damage to the laminate and/or the mold member during a separation process, and/or susceptibility to breakage, so as to be incapable of reuse. The improvement over the Peetz et al. arrangement involves replacing the rigid glass protective member by a composite protective layer that is flexible. More specifically, the laminate is manufactured by assembling into a stack, a sheet of glass, which may be tempered, a sheet of plastic, and the composite protective layer comprising a thin flexible protective sheet and a thick cushion sheet, with the combined sheet thickness being in a range on the order of 6 to 33 mm. The stack is enclosed in a bag of rubber or similar flexible material which is evacuated to degas the stack. The bag with the stack therein is then subjected to heat and pressure in an autoclave to bond together the glass and plastic sheets, whereafter the protective and cushion sheets can be separated from the remainder of the stack.
U.S. Pat. No. 4,232,080 to Orain et al. discloses a safety window comprising at least one sheet of glass, which may be tempered, and on the other side thereof facing the interior of the vehicle in which the window is to be mounted, a sheet of transparent, elastic plastic material, such as aliphatic polyurethane, bonded adhesively to the glass sheet. According to the patent, a prior art embodiment also includes a sheet of tempered glass having bonded thereto a sheet of plastic material such as polycarbonate, polyacrylate, cellulose acetate, polyester, polyvinylchloride or the like.
In the U.S. Pat. No. 5,002,820 to Bolton et al., an anti-spalling laminated safety glass is disclosed, comprising a relatively thick front lamina, a back glass lamina, and an intermediate resinous bonding layer. Any of a number of known resins can be used as outer laminae, tempered glass can be used as a glass layer, and solid resinous materials which can be used include polyesters and ABS plastics. Furthermore, an interlayer can include rigid plies of coated or uncoated glass, polycarbonate, acrylic or polyester, and/or flexible plies of polyurethane, other esters commonly used as interlayer materials, and polyvinyl butyral resin.